This invention relates to a fluid flow reverser assembly in which an inlet and an outlet for a fluid to and from the reverser assembly can be selectively coupled to either of two other inlets/outlets to and from the reverser assembly such that the latter, if connected to a shell and tube heat exchanger or the like, can receive the fluid flowing in either of the two possible directions simply by reversing the condition of the flow reverser, whilst the inlet to the assembly and the outlet therefrom do not change their condition.
Such an arrangement is particularly important in cases where heat exchangers are connected to the flow reverser and the purpose of reversing flow periodically is to move, under fluid pressure, cleaning brushes through the heat exchanger tubes in order to dislodge dirt which may become adhered to the inner surface of the heat exchanger tubes. Such flow reversers can be operated automatically at preselected time intervals and, generally speaking the flow is reversed for a relatively short period of time, but at least sufficient to enable the brushes to traverse the length of the heat exchanger tube, and thereafter to again reverse it so that the brushes return to their first positions.
As far as applicant is aware there are three different types of flow reverser assemblies available at the present time. The first is termed a four-way valve (often referred to as a "H"-type valve) in which a rotatable plug in a body therefor is rotatable simply to divert the incoming fluid to either of two possible passages out of which it can flow initially. These four-way valves employ a clearance seal, that is to say there is no positive seal, and accordingly have leakage associated therewith. Also they have a high pressure drop across the valve due to the fact that each of the inlets/outlets, communicates with a chamber within the valve body and, accordingly, no smooth flow path is provided in either of the directions of flow.
The second type of valve which is available is what is termed a switch pipe valve in which an extremely long vane and pipe combination seals longitudinally between two chambers through which fluid flows in each of the two possible directions. In order to reverse the flow, the pipe is moved angularly so that the vane no longer seals but the ends of the pipe are in clearance sealing co-operation with diagonally located inlet/outlet passages. Again a high pressure drop is associated with such a flow reverser assembly or valve in view of the fact that both the incoming and outgoing fluids pass through enlarged chambes having shapes not conducive to smooth fluid flow. Once again clearance type seals are employed which leads to leakage.
A third type of valve or flow reverser assembly which is available is that which may be termed a multi-port cylinder valve. Once again a clearance seal is used (although with not as great a disadvantage as the aforegoing two types of flow reverser assemblies) but the multi-port cylinder has a substantial pressure drop associated therewith in view of the rather tortuous paths through which the fluid must flow. Also, such a valve is difficult to manufacture in view of the relatively close tolerances and large size of clearance fit sealing surfaces which are present.